Preparation of alkylamides

ABSTRACT

A method of preparing alkylamides which comprises contacting an ammonium, Group IA or group IIA metal salt of a terminal alphanitroketone with an acidic mineral acid salt in a carboxylic acid solvent.

United States Patent Kablaoui et a1.

[ Dec. 16, 1975 PREPARATION OF ALKYLAMIDES Inventors: Mahmoud S. Kablaoui, Wappingers Falls; Roger G. Duranleaii, Ardonia, both of N.Y.

Assignee: Texaco Inc., New York, N.Y.

Filed: Dec. 12, 1974 Appl. No.: 532,266

US. Cl. 260/404; 260/561 R Int. Cl. C07C'103/02 Field of Search 260/561 R, 404

References Cited UNITED STATES PATENTS 3,551,465 12/1970 Ellis 260/404 2/1971 Ellis 260/561 R 11/1973 Lang i 260/404 12/1973 Kelly et al...... 260/561 R 1/1975 Love et a1. 260/561 R Primary ExaminerC. Davis Attorney, Agent, or FirmT. H. Whaley; C. G. Ries; George J. Darsa ABSTRACT 27 Claims, No Drawings PREPARATION OF ALKYLAMIDES BACKGROUND OF THE INVENTION This invention relates to a novel method of preparing alkylamides and particularly to the preparation of alkylamides from salts of terminal alpha-nitroketones.

Alkylamides have previously been prepared by such classical methods as the amination of carboxylic acids. Many carboxylic acids, however, are not readily available, particularly those containing an odd number of carbon atoms and relatively expensive reactants are required to obtain the same. For example, the acids can be produced by oxidizing the corresponding alcohol or by employing a Grignard synthesis, but such methods require costly starting materials. Other routes for preparing alkylamides, such as the conversion of nitronitrosoalkane dimers by reaction with at least molar amounts of an anhydrous mineral acid for relatively short contact times is not commercially attractive inasmuch as the mineral acid is consumed in the course of the reaction and the concentration of the charge in the strong acid must be kept low to avoid explosive conditions. Further, the reaction is water sensitive and the alkylamides are hydrolyzed to the corresponding acids. Moreover, the amount of concentrated acid employed in such a method requires the use of costly corrosion resistant equipment.

We have now found a method whereby a range of individual or mixtures of alkylamides having from 2 to 51 carbon atoms can be produced in exceptionally good yields, which method can be conducted in less costly equipment.

. SUMMARY OF THE INVENTION pha-nitroketone converted to the alkylamide corresponds to the formula:

where R is an alkyl group having from 1 to 50 carbon atoms, suitably from 3 to 40 carbons and preferably to 30 carbons, where A is NH a Group IA metal or a Group IIA metal and where n is l or 2. Illustrative of the Group IA metals are lithium, sodium and potassium and of the Group IIA metals we mention magnesium, calcium, strontium and barium. The preferred nitroketone salts are those of ammonium, sodium, calcium and magnesium. It is essential to the method of this invention that the salts of terminal alpha-nitroketones, i.e., 1-n1tro-2-alkanones, be employed. Salts of non-tenninal alpha-nitroketones, that is nitroketones where the nitro group is on other than a terminal carbon atom, do not undergo the conversion to alkylamides as herein more fully described.

The method contemplated by this invention is further explained by the following equation:

where R is as heretofore defined and where a by-product of the method is carbon dioxide. From the equation it will be seen that the alkylamide formed by the 0 method possesses one carbon less than the starting salt of the nitroketone, such that the reaction involves transformation of the salt to the amide through rearrangement and cleavage. Illustration of the alkylamides prepared by the instant method we mention acetamide, propanamide, butanamide, pentanamide, heptanamide, octanamide, nonanamide, decanarnide, undecanamide, tridecanamide, tetradecanamide, pentadecanamide and eicosanamide.

Pursuant to this invention, the alkylamides are prepared from salts of alpha-nitroketones corresponding to the formula above and include as starting materials the following ammonium salts ammonium l-nitro-2- propanone, ammonium l-nitro-Z-butanone, ammonium l-nitro-2-pentanone, ammonium l-nitro-2-hexanone, ammonium l-nitro-2-heptanone, ammonium l-nitro-2-octanone, ammonium l-nitro-2-decanone, ammonium l-nitro-Z-dodecanone, ammonium l-nitro- Z-pentaclecanone, ammonium l-nitro-2-hexadecanone, ammonium l-nitro-2-heptadecanone, and ammonium I-nitro-Z-eicosanone. Mixtures of ammonium salts of nitroketones can also be employed and provide as product mixtures of alkylamides. The corresponding Group IA and Group IIA metal salts are also contemplated such as sodium l-nitro-2-propanone, potassium l-nitro-2-butanone, lithium l-nitro-2-pentanone, magnesium I-nitro-Z-hexanone, calcium l-nitro-2-octanone, barium 1-nitro-2-decanone, strontium l-nitro-2- hexadecanone as well as mixtures of Group IA or Group IlA saltsof nitroketones. The half salts of the Group II metals are also contemplated by the instant method.

The salts of alpha-nitroketones contemplated as starting materials and illustrated above can be prepared from l-olefins corresponding to the formula:

R CH cn where R is as heretofore defined by simultaneously contacting the olefin with dinitrogen tetroxide and oxygen at a temperature between about -40 and 20C. employing a mole ratio to olefin to dinitrogen tetroxide to oxygen of between about 110.511 and 121.5:30 to form a peroxy compound of the formula:

OONO

R- l-I-Cl-hNO:

where R is as heretofore defined, and thereafter contacting the peroxy compound with a denitrating agent of the type known to the art, such as dimethylformamide, diethylformamide, dimethylacetamide, dimethylsulfoxide, diethylsulfoxide, tetramethylurea, tetracthylurea, hexamethylene-phosphoramide, l-methyl-Z- pyrrolidinone, l-ethyl-2-pyrrolidinone, l-isobutyl-2- pyrrolidinone and 1,3dimethyl-2pyrrolidinone. The contacting with a denitrating agent is undertaken under conditions of agitation and at a temperature of between about 60 and C. using a mole ratio of denitrating agent to peroxy compound of about 1:1 to about 20:1

to form a l-nitro-2-alkanone. The alpha-nitroketone product can be recovered by standard recovery procedures, for example by filtration of the solid intermediate after the addition of the reaction mixture to water or by distillation. The nitroketone is converted to the corresponding salt by contacting the nitroketone with from about 1 to about moles of ammonia, a Group IA metal hydroxide or Group IIA metal oxide or bydroxide per mole of nitroketone at a temperature of about l0 to 330C.

In one embodiment, the method of this invention comprises heating the salt of the nitroketone as heretofore described at a temperature of from about 60 to 200C., preferably from about 75 to 130C., with an acidic mineral acid salt in the presence of a monocarboxylic acid as solvent. Acidic mineral acid salts contemplated as catalysts herein include ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium hydrogen sulfate, ammonium phosphate, aluminum nitrate, aluminum sulfate, ferric chloride, cupric nitrate, zinc sulfate and calcium nitrate. Other salts such as calcium chloride and calcium sulfate do not function in the same manner and reactions employing the same fail to cause the desired reaction. In highly preferred embodiments, we employ ammonium nitrate or calcium nitrate. The mole ratio of nitroketone salt to acidic mineral acid salt employed herein can range from about 110.01 to 1:2 and we prefer to employ ranges of from about 1:0.1 to 1:1. While substantially anhydrous conditions need not be employed in the method, we prefer that the water content in the reaction be maintained below about 3 percent as the same deters hydrolysis of the amide, particularly when the higher reaction temperatures are employed.

As described herein, the rearrangement and transformation of the salt of the nitroketone to the alkylamide is conducted in the presence of a monocarboxylic acid suitably having from 1 to 16 carbon atoms, as for example formic acid, acetic acid, propionic acid, isobutanoic acid, pentanoic acid, hexanoic acid, octanoic acid, decanoic acid, undecanoic acid, dodecanoic acid and hexadecanoic acid and we prefer to employ carboxylic acids having from 1 to 6 carbon atoms, such as formic, acetic or propionic acids. A particularly preferred acid is acetic acid. The carboxylic acid solvent assists in solubilizing the salt of the nitroketone thereby ensuring a good contact between the reactants. The carboxylic acid solvent is generally employed in our method in a mole ratio of salt of nitroketone to solvent of about 1: 1 to 1:100, preferably about 1:4 to 1:40. The use of the solvent contributes to improved yields of alkylamide and permits the reaction to be substantially completed in from about one-quarter to three hours, although longer reaction times may be employed. At the completion of the rearrangement and cleavage reaction, the reaction mixture is cooled to about room temperature and the alkylamide can be recovered by for example, filtration of the product after the addition of the reaction mixture to water or the alkylamide can be separated from the mixture by distillation.

In a particularly preferred embodiment of this invention, a method is contemplated for preparing alkylamides wherein a l-olefin having from 3 to 52 carbons, or a mixture of l-olefins, is initially nitrooxidized as described above with dinitrogen tetroxide and oxygen to form a nitroalkylperoxy nitrate, the nitroalkylperoxy nitrate is thereafter contacted with a denitrating agent to form a crude composition comprising a mixture of the nitroketone and denitrating agent along with byproducts nitric acid, and the corresponding nitronitrate and nitroalcohol. This crude composition is thereafter contacted with about 1 to about 10, preferably 1 to 2.5 moles of ammonia, Group I metal hydroxide or Group IIA metal oxide or hydroxide per mole of nitroketone at a temperature of about l0 to 30C. In the course of contacting the crude composition with the basic material such as ammonia or calcium oxide, the base reacts with nitric acid in the crude composition to form the corresponding nitrate salt, such as ammonium nitrate or calcium nitrate, and with the nitroketone to yield its salt, such as the ammonium or calcium salt of the nitroketone. The salts of the nitroketone and nitric acid are insoluble in the crude composition and can be easily separated therefrom, if desired, employing any well-known technique, as for example by filtration, centrifugation, decantation, etc. The filtrate, if separated from the insoluble salts, comprises the denitrating agent and by-products, nitronitrates and nitroalcohols, each of which are soluble and do not react with the base such as ammonia or calcium oxide. To the salts of the nitroketone and nitric acid, there is introduced a monocarboxylic acid of the type described above in an amount of about 1 to 100 moles, preferably 4 to 40 moles, of carboxylic acid per mole of nitroketone salt and the reaction mixture is heated as previously described thereby cleaving and rearranging the salt of the nitroketone to the alkylamide. At the completion of the reaction, the alkylamide is recovered by cooling the reaction mixture and isolating the resulting solid by filtration or by diluting the mixture with water at below 60C. and recovering the crystals of amide. The coproduct, carbon dioxide, can be recovered if desired in the course of the reaction or at the completion thereof by scrubbing the exit gas with an amine base at room temperature and thereafter thermally decomposing the amine-carbon dioxide complex.

By the instant method, salts of nitroketones can be essentially quantitatively converted to the amide and high conversions and selectivities to the amide of percent and higher have been realized.

The alkylamides prepared according to this invention are useful as ore flotation agents, foam stabilizers in synthetic detergents, solvents for waxes, dye solubilizers, plasticizers for polymers, surfactants, dispersants or diluents for reactions and in the production of carbon paper, rubber and wax paper as well as intermediates in the preparation of fabric water repellants.

In order to more fully illustrate the nature of our invention and the manner of practicing the same, the following examples are presented.

EXAMPLE I Into a 300 milliliter flask equipped with a gas inlet thermometer and condenser, there was charged 22.4 grams (0.1 mole) of a l-hexadecene and milliliters of carbon tetrachloride. To this solution, maintained at a temperature of about 5l0C., there was introduced oxygen at the rate of 60-80 milliliters per minute and 9.2 grams (0.1 mole) of dinitrogen tetroxide at the rate of 0.05 gram per minute over a period of 3 hours. At the end of the dinitrogen tetroxide-oxygen addit on period, 19.8 grams (0.2 mole) of l-methyl-2-pyrrol1d1- none as denitrating agent were added over a period of one-half hour while maintaining the temperature at 5l0C.

To the above reaction mixture, maintained at 20C., there was introduced 4.2 grams (0.25 mole) of ammonia as a gas at the rate of 0.14 gram per minute over a period of 30 minutes. The solids composed of ammonium nitrate and the ammonium salt of l-nitro-2-hexadecanone were separated from the crude composition by filtration and weighed 360 grams. To the solids, there was added 300 milliliters of acetic acid and the mixture was heated at 118C. for 3 hours. The solution was cooled to room temperature, 500 milliliters of water added thereto and the solids filtered and dried. 22.9 grams corresponding to a yield of 95 percent of pentadecanamide were recovered in a purity of 9 percent. I

EXAMPLE II Example I was repeated except that 6.72 grams (0.12 mole) of calcium oxide were added to the reaction mixture over a period of 30 minutes in place of ammonia. The solids composed of calcium nitrate and the calcium salt of 1-nitro-2-hexadecanone were separated from the crude mixture by filtration and weighed 39.0 grams. There was added to the solids 300 milliliters of acetic acid the mixture was heated for 3 hours at 118C. After cooling the reaction mixture to room temperature, 500 milliliters of water were added, and the solids were filtered and dried. As in Example I, 22.9 grams (95 percent yield) of pentadecanamide were recovered in a purity of 99 percent.

EXAMPLE III Example I was repeated except that after the addition of the denitrating agent, the reaction mixture was washed with three 100 milliliter portions of water to remove the denitrating agent and nitric acid. The calcium salt of l-nitro-2-hexadecanone was formed by adding 3.36 grams (0.06 mole) of calcium oxide and after isolation of the calcium salt there was added 300 milliliters of acetic acid and the mixture heated for 3 hours at 118C. After recovering the solids as in Example I, the material (20.8 grams, 92.5 percent recovery) was identified as l-nitro-2-hexadecanone indicating that no reaction had occurred.

EXAMPLE IV Example 111 was repeated except that 2.2 grams (0.23 mole) of ammonia was used in place of calcium oxide. The isolated material (20.8 grams, 92.5 percent recovery) was identified as l-nitro-2-hexadecanone thereby demonstrating that no reaction had occurred.

EXAMPLE V Example 111 was repeated except that 1 1.3 grams (0.1 mole) of calcium chloride was added to the calcium salt of 1-nitro-2-hexadecanone-acetic acid reaction mixture. As in Example 111, the product recovered was l-nitro-2-hexadecanone and this example illustrates that calcium chloride is ineffective as a catalyst for amide formation.

EXAMPLE VI Example IV was repeated except that 11.3 grams (0.1 mole) of calcium chloride was added to the ammonium salt of 1-nitro-2-hexadecanone-acetic acid reaction mixture. The results were the same as in Example V.

l EXAMPLE V11 Examples and VI were respectively repeated except that 13.6 grams (0.1 mole) of calcium sulfate were used in place of'c'alciur'n chloride. No conversion to the amide was detected, and the product isolated in each instance was 1'-nitro-2-hexadecanone. Calcium sulfate is ineffective as a catalyst for amide formation.

EXAMPLE VIII Example V was repeated except that 11.3 grams (0.1 mole) of calcium chloride and 0.6 grams of nitric acid were added to the calcium salt of l-nitro-2-hexadecanone-acetic acidreaction mixture. As in Example V, the product isolated was 1-nitro-2-hexadecanone.

We claim:

1. A method of preparing an alkylamide which comprises contacting an ammonium, Group IA or Group IIA metal salt of an alpha-nitroketone with an acidic mineral acid salt in the presence of a carboxylic acid solvent. I

2. A method according to claim 1 wherein said contacting is at a temperature of about 60 to 200C.

3. A method according to claim 1 wherein said contacting is at a temperature of about to C.

4. A method according to claim 1 wherein the mole ratio of said nitroketone salt to said acidic salt is from about 1:0.01 to 1:2.

5. A method according to claim 1 where the mole ratio of said nitroketone salt to said acid salt is from about 1:01 to 1:1.

6. A method according to claim 1 where said salt of the nitroketone corresponds to the formula:

where R is an alkyl group of from 1 to 50 carbon atoms where A is NH a Group IA metal or a Group IlA metal and where n is l or 2.

7. A method according to claim 6 wherein R is 3 to 40 carbons.

8. A method according to claim 6 wherein R is 5 to 30 carbons.

9. A method according to claim 1 wherein said nitroketone salt is ammonium 1-nitro-2-hexadecanone.

10. A method according to claim 1 wherein said nitroketone salt is ammonium 1-nitro-2-octadecanone.

11. A method according to claim 1 wherein said nitroketone salt is calcium l-nitro-2-hexadecanone.

12. A method according to claim 1 wherein said carboxylic acid has from 1 to 16 carbon atoms.

13. A method according to claim 1 wherein said carboxylic acid has from 1 to 6 carbon atoms.

14. A method according to claim 1 wherein said carboxylic acid is acetic acid.

15. A method according to claim 1 wherein said acidic salt is ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium hydrogen sulfate, aluminum nitrate, aluminum sulfate, ferric chloride, cu-

pric nitrate, zinc sulfate or calcium nitrate.

7 18. A method according to claim 1 wherein said acid salt is ammonium chloride.

19. A method according to claim I wherein said acid salt is ammonium phosphate.

20. A method according to claim 1 wherein said acid salt is calcium nitrate.

21. A method of preparing an alklyamide which comprises:

a. nitrooxidizing a l-olefin to a nitroalkylperoxy nitrate; b. denitrating said peroxy nitrate to an alpha-nitroketone; c. converting said nitroketone to its corresponding ammonium, Group 1A or Group "A metal salt and d. contacting said nitroketone salt with an acidic mineral acid salt in the presence of a carboxylic acid solvent.

22. A method according to claim 21 wherein said nitroketone and nitric acid are together converted to their corresponding ammonium salts in step (c).

23. A method according to claim 21 wherein said nitroketone and nitric acid are together converted to their corresponding calcium salts in step (c).

24. A method according to claim 21 wherein said contacting in (d) is at a temperature of about 60 to 200C.

25. A method according to claim 21 wherein said contacting in (d) is at a temperature of about to C.

26. A method according to claim 21 wherein said carboxylic acid solvent has from 1 to 16 carbon atoms.

27. A method according to claim 21 wherein said carboxylic acid is acetic acid. 

1. A METHOD OF PREPARING AN ALKYLAMIDE WHICH COMPRISES CONTACTING AN AMMONIUM, GROUP IA OR GROUP IIA METAL SALT OF AN ALPHA-NITROKETONE WITH AN ACIDIC MINERAL ACID SALT IN THE PRESENCE OF A CARBOXYLIC ACID SOLVENT.
 2. A method according to claim 1 wherein said contacting is at a temperature of about 60* to 200*C.
 3. A method according to claim 1 wherein said contacting is at a temperature of about 75* to 130*C.
 4. A method according to claim 1 wherein the mole ratio of said nitroketone salt to said acidic salt is from about 1:0.01 to 1:2.
 5. A method according to claim 1 where the mole ratio of said nitroketone salt to said acid salt is from about 1:0.1 to 1:1.
 6. A method according to claim 1 where said salt of the nitroketone corresponds to the formula:
 7. A method according to claim 6 wherein R is 3 to 40 carbons.
 8. A method according to claim 6 wherein R is 5 to 30 carbons.
 9. A method according to claim 1 wherein said nitroketone salt is ammonium 1-nitro-2-Hexadecanone.
 10. A method according to claim 1 wherein said nitroketone salt is ammonium 1-nitro-2-octadecanone.
 11. A method according to claim 1 wherein said nitroketone salt is calcium 1-nitro-2-hexadecanone.
 12. A method according to claim 1 wherein said carboxylic acid has from 1 to 16 carbon atoms.
 13. A method according to claim 1 wherein said carboxylic acid has from 1 to 6 carbon atoms.
 14. A method according to claim 1 wherein said carboxylic acid is acetic acid.
 15. A method according to claim 1 wherein said acidic salt is ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium hydrogen sulfate, aluminum nitrate, aluminum sulfate, ferric chloride, cupric nitrate, zinc sulfate or calcium nitrate.
 16. A method according to claim 1 wherein said acidic salt is ammonium nitrate.
 17. A method according to claim 1 wherein said acid salt is ammonium sulfate.
 18. A method according to claim 1 wherein said acid salt is ammonium chloride.
 19. A method according to claim 1 wherein said acid salt is ammonium phosphate.
 20. A method according to claim 1 wherein said acid salt is calcium nitrate.
 21. A method of preparing an alklyamide which comprises: a. nitrooxidizing a 1-olefin to a nitroalkylperoxy nitrate; b. denitrating said peroxy nitrate to an alpha-nitroketone; c. converting said nitroketone to its corresponding ammonium, Group IA or Group IIA metal salt and d. contacting said nitroketone salt with an acidic mineral acid salt in the presence of a carboxylic acid solvent.
 22. A method according to claim 21 wherein said nitroketone and nitric acid are together converted to their corresponding ammonium salts in step (c).
 23. A method according to claim 21 wherein said nitroketone and nitric acid are together converted to their corresponding calcium salts in step (c).
 24. A method according to claim 21 wherein said contacting in (d) is at a temperature of about 60* to 200*C.
 25. A method according to claim 21 wherein said contacting in (d) is at a temperature of about 75* to 130*C.
 26. A method according to claim 21 wherein said carboxylic acid solvent has from 1 to 16 carbon atoms.
 27. A method according to claim 21 wherein said carboxylic acid is acetic acid. 